These days, there are various kinds of wireless communication systems such as wireless LAN system based on IEEE 802.11a/g, DSRC system using amplitude modulation, Bluetooth, etc. Since communication of each wireless communication system is based on each wireless communication scheme, a communication device corresponding to a certain wireless communication system generally cannot communicate with a communication device corresponding to another wireless communication system. A user wishing to use a plurality of wireless communication systems has to have own communication devices corresponding to respective wireless communication systems.
A communication device corresponding to a plurality of wireless communication systems is useful, but such a communication device has to include modulators corresponding to the plurality of communication systems. In this case, since a plurality of modulators are required, the size and cost of the device are increased.
There existed a digital modulation device including a QPSK baseband processor and an ASK baseband processor, in which a controller determines which baseband processor should be used to transmit a signal.
A conventional transmitter capable of communicating with a first wireless communication system and a second wireless communication system each being based on a different modulation scheme has to include the functions of both of the wireless communication systems separately, which leads to a problem of increase in size and cost of the device.